U3506 code meaning
Control Module Input Power B Circuit High
Network system Generic code U35xx codes Check engine light
What U3506 means
U3506 reports overvoltage on supply input B. In GM's electric brake booster (2016–2019 hybrid OBD tables) three checks feed this code: battery voltage of the booster circuit above 17 V for 90 s, the supply of the internal motor driver above 18 V for 1.1 s, and battery voltage above 16.5 V for 1.1 s, at which booster performance is cut back. All are Type B, MIL after two trips; passing takes 90 s with ignition on. The graded limits reveal the idea: brief excursions are tolerated, lasting ones or those that put the power stage at risk are not. Check the charging voltage at idle with loads switched on first, then external chargers, jump starters and loose battery terminals that produce voltage spikes.
U3506 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U3506
- MIL after two trips
- Reduced assist of the supplied power stage
- Overvoltage codes in further modules
Common causes of U3506
- Most likelyCharging voltage too high from regulator or DC/DC converter
- PossibleJump starter or charger delivering excessive voltage
- PossibleLoose battery terminal causing spikes
- Less likelyFaulty measurement of feed B in the module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Module power bCharging system
What each part of U3506 means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 06 | The exact fault in that area. |
What to do next
- Note U3506 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U3506
What does U3506 mean?
U3506 means "Control Module Input Power B Circuit High". U3506 reports overvoltage on supply input B. It is a generic code, so it means the same on every make.
Is it safe to drive with U3506?
Drive gently and only to a workshop. With U3506 the car can go into limp mode (reduced power) to protect itself.
Will U3506 fail an emissions test?
U3506 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U3506 to fix?
Difficulty: medium. A typical repair takes 0.3 to 2.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will U3506 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.